1. Field of the Invention
The present invention relates to a hydrogen sulfide generation-suppressed catalyst.
2. Description of the Related Art
Various catalysts are conventionally used to purify exhaust gas of automobiles. An example of widely used exhaust gas-purifying catalysts is a three-way catalyst, which is made of a precious metal such as platinum and an inorganic oxide such as ceria or alumina that supports the precious metal. However, since automotive fuels contain sulfur (S), hydrogen sulfide (H2S) is generated due to catalytic reaction when the catalyst is exposed to a reducing atmosphere. For this reason, the catalyst has a drawback of emitting an offensive odor.
A solution to this is proposed in Jpn. Pat. Appln. KOKAI Publication No. 63-310637, which describes a reduction of H2S emission by adding nickel (Ni) to the catalyst. Another solution is proposed in Jpn. Pat. Appln. KOKAI Publication No. 8-290063, which discloses an exhaust gas-purifying catalyst containing nickel oxide.
However, at present, in several countries especially in Europe, Ni and Ni compounds are designated as materials that load on the environment and the use of Ni or a Ni compound in a catalyst is prohibited. Under the circumstances, there is a demand for means that can reduce H2S emission without using Ni and significantly deteriorating the exhaust gas-purifying ability.